This invention relates to improved pressurized ducting systems for delivery of anti-ice air to aircraft leading edge slats actuated to move between retracted, stowed position and extended, operating position. The improved ducting system is herein illustratively described by reference to the presently preferred embodiment thereof, but it will be recognized that certain modifications and changes therein with respect to details may be made without departing from the essential features involved.
Problems experienced with existing ducting systems for delivering anti-ice air to leading edge slats arise primarily in the transfer ducting, that is, in the sets of telescoping inner and outer ducts that transfer pressurized warm air from the supply duct running lengthwise in the wing's leading edge to the spray ducts running lengthwise in the deployable slats and having openings through which warm air is delivered to the interior surface of the slat. When extended, the inner transfer duct of each set is exposed to rain and slush, and with the metal below freezing temperature, tends to accumulate a buildup of ice. It also tends to accumulate dirt and sometimes particles of metal which cause wear of bearings and seals, and which can be picked up by the bearing surfaces to causing galling of duct surfaces. In fact, at times ice accumulation can become so thick as to impede or even cause buckling of the thin-wall (essentially sheet metal) inner and outer ducts during slat retraction. Also, wear of bearing surfaces over a period of time and lateral loading on the telescoping transfer ducts during slat retraction, such as caused, for example, by slat movements during flight, can impede smooth retraction and can generate buckling stresses in the transfer ducts. These problems became chronic with prior flow transfer duct apparatus. Strengthening the tubes adds both cost and weight and alone was not a full solution.
The present invention is directed toward overcoming these problems and limitations without adding materially to cost and weight of the ducting system. More specifically, it is an object here to protect the slide bearings and seal means in a simple and reliable duct construction more durable, wear-free and failure-proof duct than the prior means for transferring anti-ice air from a supply duct in the wing to a spray duct in the slat. In so doing, the invention provides an improved bearing and seal arrangement for the telescoping transfer ducts which will assure their self-alignment under all ambient conditions and operating conditions.